U.S. Pat. No. 5,594,052 discloses a method for increasing the rate of vulcanization of a sulfur vulcanizable rubber by using a hydrated thiosulfate. Specific examples of hydrated thiosulfates include BaS.sub.2 O.sub.3.H.sub.2 O, K.sub.2 S.sub.2 O.sub.3. 1.5 H.sub.2 O, CaS.sub.2 O.sub.3.6H.sub.2 O, MgS.sub.2 O.sub.3.6H.sub.2 O, NiS.sub.2 O.sub.3.6H.sub.2 O, CoS.sub.2 O.sub.3.6H.sub.2 O, SrS.sub.2 O.sub.3.5H.sub.2 O, Na.sub.2 S.sub.2 O.sub.3.5H.sub.2 O, MnS.sub.2 O.sub.3.5H.sub.2 O, Li.sub.2 S.sub.2 O.sub.3.3H.sub.2 O and CdS.sub.2 O.sub.3.2H.sub.2 O.
EP 765903-A2 discloses an adherent rubber composition for steel cord containing 0.1 to 10 parts by weight of an inorganic salt hydrate. Representative examples of inorganic salt hydrates include NiSO.sub.4.7H.sub.2 O, CoSO.sub.4.7H.sub.2 O, CaSO.sub.4.2H.sub.2 O, ZnSO.sub.4.7H.sub.2 O, MgSO.sub.4.7H.sub.2 O and Na.sub.2 S.9H.sub.2 O.